1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
4--                                                                          --
5--     S Y S T E M . T A S K I N G . R E S T R I C T E D . S T A G E S      --
6--                                                                          --
7--                                  S p e c                                 --
8--                                                                          --
9--          Copyright (C) 1992-2012, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNARL is free software; you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNARL was developed by the GNARL team at Florida State University.       --
28-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This is a simplified version of the System.Tasking.Stages package,
33--  intended to be used in a restricted run time.
34
35--  This package represents the high level tasking interface used by the
36--  compiler to expand Ada 95 tasking constructs into simpler run time calls
37--  (aka GNARLI, GNU Ada Run-time Library Interface)
38
39--  Note: the compiler generates direct calls to this interface, via Rtsfind.
40--  Any changes to this interface may require corresponding compiler changes
41--  in exp_ch9.adb and possibly exp_ch7.adb
42
43--  The restricted GNARLI is also composed of System.Protected_Objects and
44--  System.Protected_Objects.Single_Entry
45
46with System.Task_Info;
47with System.Parameters;
48
49package System.Tasking.Restricted.Stages is
50   pragma Elaborate_Body;
51
52   ---------------------------------
53   -- Compiler Interface (GNARLI) --
54   ---------------------------------
55
56   --  The compiler will expand in the GNAT tree the following construct:
57
58   --   task type T (Discr : Integer);
59
60   --   task body T is
61   --      ...declarations, possibly some controlled...
62   --   begin
63   --      ...B...;
64   --   end T;
65
66   --   T1 : T (1);
67
68   --  as follows:
69
70   --   task type t (discr : integer);
71   --   tE : aliased boolean := false;
72   --   tZ : size_type := unspecified_size;
73
74   --   type tV (discr : integer) is limited record
75   --      _task_id : task_id;
76   --      _atcb : aliased system__tasking__ada_task_control_block (0);
77   --   end record;
78
79   --   procedure tB (_task : access tV);
80   --   freeze tV [
81   --      procedure tVIP (_init : in out tV; _master : master_id;
82   --        _chain : in out activation_chain; _task_name : in string;
83   --        discr : integer) is
84   --      begin
85   --         _init.discr := discr;
86   --         _init._task_id := null;
87   --         system__tasking__ada_task_control_blockIP (_init._atcb, 0);
88   --         _init._task_id := _init._atcb'unchecked_access;
89   --         create_restricted_task (unspecified_priority, tZ,
90   --           unspecified_task_info, unspecified_cpu,
91   --           task_procedure_access!(tB'address), _init'address,
92   --           tE'unchecked_access, _task_name, _init._task_id);
93   --         return;
94   --      end tVIP;
95
96   --   _chain : aliased activation_chain;
97   --   activation_chainIP (_chain);
98
99   --   procedure tB (_task : access tV) is
100   --      discr : integer renames _task.discr;
101
102   --      procedure _clean is
103   --      begin
104   --         complete_restricted_task;
105   --         finalize_list (F14b);
106   --         return;
107   --      end _clean;
108
109   --   begin
110   --      ...declarations...
111   --      complete_restricted_activation;
112   --      ...B...;
113   --      return;
114   --   at end
115   --      _clean;
116   --   end tB;
117
118   --   tE := true;
119   --   t1 : t (1);
120   --   t1S : constant String := "t1";
121   --   tIP (t1, 3, _chain, t1S, 1);
122
123   Partition_Elaboration_Policy : Character := 'C';
124   pragma Export (C, Partition_Elaboration_Policy,
125                  "__gnat_partition_elaboration_policy");
126   --  Partition elaboration policy. Value can be either 'C' for concurrent,
127   --  which is the default or 'S' for sequential. This value can be modified
128   --  by the binder generated code, before calling elaboration code.
129
130   procedure Create_Restricted_Task
131     (Priority      : Integer;
132      Stack_Address : System.Address;
133      Size          : System.Parameters.Size_Type;
134      Task_Info     : System.Task_Info.Task_Info_Type;
135      CPU           : Integer;
136      State         : Task_Procedure_Access;
137      Discriminants : System.Address;
138      Elaborated    : Access_Boolean;
139      Chain         : in out Activation_Chain;
140      Task_Image    : String;
141      Created_Task  : Task_Id);
142   --  Compiler interface only. Do not call from within the RTS.
143   --  This must be called to create a new task, when the partition
144   --  elaboration policy is not specified (or is concurrent).
145   --
146   --  Priority is the task's priority (assumed to be in the
147   --  System.Any_Priority'Range)
148   --
149   --  Stack_Address is the start address of the stack associated to the task,
150   --  in case it has been preallocated by the compiler; it is equal to
151   --  Null_Address when the stack needs to be allocated by the underlying
152   --  operating system.
153   --
154   --  Size is the stack size of the task to create
155   --
156   --  Task_Info is the task info associated with the created task, or
157   --  Unspecified_Task_Info if none.
158   --
159   --  CPU is the task affinity. We pass it as an Integer to avoid an explicit
160   --   dependency from System.Multiprocessors when not needed. Static range
161   --   checks are performed when analyzing the pragma, and dynamic ones are
162   --   performed before setting the affinity at run time.
163   --
164   --  State is the compiler generated task's procedure body
165   --
166   --  Discriminants is a pointer to a limited record whose discriminants are
167   --  those of the task to create. This parameter should be passed as the
168   --  single argument to State.
169   --
170   --  Elaborated is a pointer to a Boolean that must be set to true on exit
171   --  if the task could be successfully elaborated.
172   --
173   --  Chain is a linked list of task that needs to be created. On exit,
174   --  Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID will be
175   --  Created_Task (the created task will be linked at the front of Chain).
176   --
177   --  Task_Image is a string created by the compiler that the run time can
178   --  store to ease the debugging and the Ada.Task_Identification facility.
179   --
180   --  Created_Task is the resulting task.
181   --
182   --  This procedure can raise Storage_Error if the task creation fails
183
184   procedure Create_Restricted_Task_Sequential
185     (Priority      : Integer;
186      Stack_Address : System.Address;
187      Size          : System.Parameters.Size_Type;
188      Task_Info     : System.Task_Info.Task_Info_Type;
189      CPU           : Integer;
190      State         : Task_Procedure_Access;
191      Discriminants : System.Address;
192      Elaborated    : Access_Boolean;
193      Task_Image    : String;
194      Created_Task  : Task_Id);
195   --  Compiler interface only. Do not call from within the RTS.
196   --  This must be called to create a new task, when the sequential partition
197   --  elaboration policy is used.
198   --
199   --  The parameters are the same as Create_Restricted_Task_Concurrent,
200   --  except there is no Chain parameter (for the activation chain), as there
201   --  is only one global activation chain, which is declared in the body of
202   --  this package.
203
204   procedure Activate_Restricted_Tasks
205     (Chain_Access : Activation_Chain_Access);
206   --  Compiler interface only. Do not call from within the RTS.
207   --  This must be called by the creator of a chain of one or more new tasks,
208   --  to activate them. The chain is a linked list that up to this point is
209   --  only known to the task that created them, though the individual tasks
210   --  are already in the All_Tasks_List.
211   --
212   --  The compiler builds the chain in LIFO order (as a stack). Another
213   --  version of this procedure had code to reverse the chain, so as to
214   --  activate the tasks in the order of declaration. This might be nice, but
215   --  it is not needed if priority-based scheduling is supported, since all
216   --  the activated tasks synchronize on the activators lock before they start
217   --  activating and so they should start activating in priority order.
218   --
219   --  When the partition elaboration policy is sequential, this procedure
220   --  does nothing, tasks will be activated at end of elaboration.
221
222   procedure Activate_All_Tasks_Sequential;
223   pragma Export (C, Activate_All_Tasks_Sequential,
224                  "__gnat_activate_all_tasks");
225   --  Binder interface only. Do not call from within the RTS. This must be
226   --  called an the end of the elaboration to activate all tasks, in order
227   --  to implement the sequential elaboration policy.
228
229   procedure Complete_Restricted_Activation;
230   --  Compiler interface only. Do not call from within the RTS. This should be
231   --  called from the task body at the end of the elaboration code for its
232   --  declarative part. Decrement the count of tasks to be activated by the
233   --  activator and wake it up so it can check to see if all tasks have been
234   --  activated. Except for the environment task, which should never call this
235   --  procedure, T.Activator should only be null iff T has completed
236   --  activation.
237
238   procedure Complete_Restricted_Task;
239   --  Compiler interface only. Do not call from within the RTS. This should be
240   --  called from an implicit at-end handler associated with the task body,
241   --  when it completes. From this point, the current task will become not
242   --  callable. If the current task have not completed activation, this should
243   --  be done now in order to wake up the activator (the environment task).
244
245   function Restricted_Terminated (T : Task_Id) return Boolean;
246   --  Compiler interface only. Do not call from within the RTS. This is called
247   --  by the compiler to implement the 'Terminated attribute.
248   --
249   --  source code:
250   --     T1'Terminated
251   --
252   --  code expansion:
253   --     restricted_terminated (t1._task_id)
254
255   procedure Finalize_Global_Tasks;
256   --  This is needed to support the compiler interface. It will only be called
257   --  by the Environment task in the binder generated file (by adafinal).
258   --  Instead, it will cause the Environment to block forever, since none of
259   --  the dependent tasks are expected to terminate
260
261end System.Tasking.Restricted.Stages;
262